What is the maximum luggage weight (checked-in, to go in the hold) when travelling to the USA?

It's normally 20 kilos but can vary depending who you are flying with and where you are coming from. I recently went around the world and was allowed 46 kilos on all flights. It should say on your ticketing other wise phone your airline

As others have said, it depends on the airline and the class of your ticket. Generally for European airlines its 20kg per passenger. Budget airlines allow less. If you have a frequent flyer card, you can take extra. But airports will not take any item that weighs over 32kg. US airlines did have higher allowances but brought in restrictions due to high fuel costs.

It varies from airline to airline but I know that Virgin Atlantic allow you 2 hold cases per person up to 20 kilos each.

It's best to check with the airline you are travelling with as baggage allowance can vary from airline to airline, many will allow 2 bags of 23kg each for economy, and first business class either 3 x 23kg or 2 x 32kg. The industry and DoT are all heading towards 23kg maximum, as this is deemed to be a safe lifting limit for baggage/aircraft loaders. Visit you chosen airlines website, and check the allowance for your class of travel.

What airline? What ticket class? Where from? There are a lot of variables here.

With Virgin you can take 2 pieces each weighing up to 23kg